In the treatment of flue gas, dry flue gas desulfurization (DFGD) systems are known. In DFGD systems, lime (CaO) is first converted to hydrated lime (Ca(OH)2) before being placed in contact with the flue gas to be treated. The hydrated lime is placed in contact with the flue gas as a dry or moistened powder within a circulating dry scrubber (CDS) DFGD system. An example of such a CDS DFGD system is the General Electric NID™ system (General Electric Company, Fairfield, Conn., USA).
WO 97/37747, invented by Stefan Ahman et al., discloses a device for a CDS DFGD system useful for discharging and distributing such a dry or moistened powder absorbent material in a flue gas duct. Accordingly, in a vertical flue gas duct, a discharging and distributing device is arranged to discharge and distribute a dry or moistened powder absorbent material reactive with the gaseous pollutants in the flue gas to produce a separable dust reaction product. Hence, through reaction with the dry or moistened powder absorbent material, gaseous pollutants in the flue gas are removed by conversion to the separable dust reaction product.
While methods and equipment capable of removing both particulate and gaseous pollutants from a flue gas stream exist, there remains a need for improved DFGD methods and equipment that are lower cost, while maintaining system stability, efficiency and effectiveness.